Clint Barton is undercover as Aaron Cross. When Outcome virals him off his greens without his knowledge, his health rapidly deteriorates from a severe mystery flu and SHIELD freaks the hell out. Clint's life hangs in the balance. Natasha is not amused by this turn of events. Clintasha.

Genre: Gen, friendship, angstRating: T for future swearingCharacters: Clint Barton as Aaron Cross, Natasha Romanoff, Phil Coulson, Nick Fury, Byer, othersPairings: Clint/NatashaSpoilers/Warnings: Pre-Avengers, pre-Bourne Legacy.Summary: Clint Barton is undercover as Aaron Cross. When they viral him off his greens, his health rapidly deteriorates from a mystery flu and SHIELD freaks the hell out. Natasha is not amused by this turn of events.

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"You'll need to take off your jacket and your shirt."

Aaron Cross took a pause from analyzing every object in the too-familiar examination room as a way to entertain himself to raise cold, calculating gray-blue eyes to the balding scientist. The man—Dr. Donald Foite—immediately dropped his eyes and shifted uncomfortably under the intensity of his gaze as sweat beaded on his brow.

It would have been amusing, if he didn't hate doctors as much as he did.

Those gray-blue eyes watched the doctor with the intensity and cold calculation befitting of a hawk as he moved around the room prepping things for Doctor Shearing. A part of him — the part that was annoyed he had to sit here like a plucked chicken awaiting an oven, completely at their mercy — took a savage amusement in the fact that Foite was looking at anything but him.

It was strange, Aaron supposed, as he pulled off his black leather jacket and gray T-shirt—seeing as his name wasn't actually Aaron. It wasn't Kenneth Kitsom, either.

In fact, Aaron Cross was just yet another alias that Clint Francis Barton had taken on over his years as an assassin for the Strategic Homeland Intervention Enforcement and Logistics Division (which Clint not-so-privately thought really needed a shorter name and/or acronym, not that Fury ever listened – SHIELD would work and sounded badass, but of course unless Fury came up with it, it was a no-go).

"Doctor Shearing will be with you shortly," Foite squeaked as he all but fled from the room, closing the door firmly behind him.

Slowly, he mentally rearranged himself from Cross to Barton and assessed everything around him with sharp eyes. He paid special attention to his file, sitting on the counter roughly eight feet away from him; nameless (of course) and adorned simply with the number five.

Internally, Clint scowled. At least where he worked, he wasn't just a number: he was an asset, an agent, a person. He had a codename and a partner and a handler, not to mention a hard-ass boss, who genuinely cared about what he did every day. As far as Fury went, it was more because he was an asset, but when it came to Phil and Natasha, it was genuine concern.

When Fury had ordered him to do this damn operation, he had almost refused—almost.

It had been Phil who eventually talked him into it, and he'd accepted on two conditions: one being that he have constant communication with his employers, which was achieved through a communication device in his false molar; and the second being a tracker that monitored his vital signs so that they would always know where he was and if he needed medical attention (and just in case Byer decided to have him killed; that too).

It had taken an extensive report of Byer's questionable morals, an extremely detailed background story, volunteering to be blown up by a planted IED, and having to pretend to be all but mentally retarded for him to "enter" the program known as Outcome.

If he was being honest, he had hated every minute of it.

Before SHIELD (because, honestly, who wanted to constantly repeat Strategic Homeland Intervention Enforcement and Logistics Division a hundred times?) he had been a hitman for a year, killing for the sake of killing, killing because he had nothing left to live for. After what had happened to him at the hands of people he once trusted, after his own damn brother nearly killed him, he had thrown in his lot with the devil and killed and killed and killed.

Clint had known that while doing so, he had slowly been destroying what was left of his soul but had been powerless to stop. He had known perfectly well that it wouldn't be long before one of his employers turned on him and he ended up dead in a random international back alley somewhere.

Phil Coulson had jerked him out of that life and had offered him a new one: a life that utilized his "unique skillset", yes, but also one that allowed him to refuse the hit if he wanted to. That was SHIELD—if they were sending him after someone, it was for a damn good reason, and he was always specifically told why Fury or the Council wanted said person dead. He was shown solid evidence and encouraged to research it on his own, because if there was one thing Fury despised, it was blind followers.

Fury appreciated his mind, appreciated his skill. Sure, he'd been pissed when Coulson dragged him into the organization snapping and glaring like a caged animal, but his flawless scores on the marksmanship tests had spoken for themselves. Fury had actually thought he was cheating, until Clint offered to do the same tests again—blindfolded and with moving targets—and got the same scores.

Coulson had stood behind him, had slowly woven cracks through the walls he had built around himself, because in Clint's mind people you trusted always turned on you, tried to kill you, left you, or all of the above. Phil hadn't done that, even after almost five years of having the man as his handler. Phil never asked too much of him, and certainly never asked him to do something he knew he couldn't handle.

For the first time since he was a very small child, someone had finally come along who cared enough to break his walls down, and for that, he owed Phil Coulson more than the older man would ever know. Because of Phil, he was finally atoning for all the red in his ledger.

Since his old life, Phil Coulson was the first person Clint had trusted wholly and completely.

Sure, Phil had to work his ass off for it, but he was a persistent bastard, Clint had to give him that. With time, Phil had become less of a handler and more of an older brother—the older brother he'd always wanted but never had.

That was valuable, and Fury had never even hinted at switching him to another handler. Of course, Phil Coulson and his never-ending patience were the only things on Earth that could handle Clint when he got into his moods or decided to defy authority with a particularly dramatic flare, but that was beside the point. It probably didn't help much that one of his favorite past time was pissing off Fury to the point that his eye twitched, mostly because he got a kick out of it every time.

Even when the Council sent him after Natasha Romanoff and Clint decided to bring her in instead of kill her, Coulson had stood firmly behind him. Oh, he hadn't been happy about it—in fact, he'd sworn up blue streak that had impressed Clint more than he cared to admit and threatened to kill him in ways that made even him wince—but all the same his words to Fury had been stern, delivered in his usual I-have-no-tolerance-for-this-bullshit-interrogation-of-my-top-agent tone.

I trust Agent Barton's judgment, sir, and if he says Romanoff will joins us, I believe him. I may not like it, and do not think for a second that he and I won't be having a conversation about this later, but I believe him. If he says she stays, she stays. I accept full responsibility for both Agent Barton and Natasha Romanoff, sir.

Clint had never accepted a mission that he hadn't thoroughly gone over with his handler first. Phil never lied to him, and he always stated his own opinions while giving Clint the information he needed to draw his own. Sure, he liked Fury, but he didn't trust fury. He trusted Phil, though. It was the least he could do, for all the repeated times Coulson had stuck his neck out for him and later, for Natasha, too.

Clint had never turned down an assignment, but he had never blindly accepted one, either. In the end, it had always been him who made the final call and took the shot with Phil's ever calm go-ahead.

And that was the problem with this assignment, Clint concluded.

Here, in this godforsaken place that he privately thought was run by a bunch of psychopath spooks, it didn't work like that. At Outcome, at the mercy of the United States government and some skinny little prick who likely sat behind a desk bitching about trivial shit all day, Clint didn't have a choice.

Outcome told him to kill and kill and kill, so he did. He hated it, he loathed it, he got sick over it—but he obeyed. He obeyed because SHIELD needed him to keep his goddamn cover.

At least he could pick and choose his targets by running them through Phil, who ran them through Fury. If they really were a threat, he took them out, usually with extreme prejudice. If not, Fury handled it and his targets vanished into new names and new lives. That, at least, made him feel a little better.

Sometimes, though, he didn't have time to do that and just had to kill kill kill. The only comfort he could garner from it was the fact that each and every name of every single victim went down on the black list against Byer and his agency spook psychobuddies.

Mostly it just made him sick that the government would order all this killing in the shadows and never own up to it; with the President in Washington blissfully unaware to the vipers that sat four seats down from him at staff meetings.

The door opening drew him from his thoughts, forcing him to abruptly shove Clint to the back of his mind and re-adorn the mask of Aaron Cross.

"Doc," he calmly greeted the pretty dark-haired woman as she entered.

"Mmm," she responded without looking at him, making a beeline for the table with his chart. "Have you been doing your blood work?"

"Like a good little soldier," he deadpanned, wishing she would at least look at him. He was antisocial by nature, but even he was starting to long for some kind of human contact. Outcome didn't let him have interactions with people at any time, ever. Well, not unless he was being sent to kill them, anyway.

It really made him miss Natasha and Phil. He flirted with Marta to keep up his usual behavior, even if he was internally imagining her a little shorter and with flaming red hair instead of brown.

Sharp eyes watched her prepping a syringe.

"Can I see your hand, please?" she requested as she finally turned to face him.

He lifted it obediently and ignored the feel of her glove-clad finger sliding gently over the rough callouses on his palms. The knife wound had scarred over and healed completely a long time ago.

She turned her back on him again and picked up the syringe, filling it expertly with a clear liquid.

His heart skipped a beat as he forced himself not to swallow. "You trying to put me down, doc?" he asked her, only half-joking, knowing perfectly well that Phil was listening to his every word on the other end of the line.

"Barton?" Phil's voice said faintly, the hint of worry there.

Momentary annoyance stabbed through him. He couldn't exactly respond with the doctor standing two feet in front of him. He would have to say it aloud, and no matter how quietly he did so, she would hear him and likely think him insane.

So, for Phil's benefit, he clicked his teeth together twice, the sign that all was well. A short moment later he heard Phil's sigh of relief and quiet order of, "Keep me posted, Clint."

Clint clicked his teeth again, just to give Phil some peace of mind. Marta's voice drew him back to the present and he refocused his entire attention on her.

"Well, I'm afraid there's been a few gaps in your sample delivery, so…"

"Uh-oh," he remarked cynically as she injected the liquid into his arm. Honesty, the hell was wrong with these lab types? As if he had time to sit down in the middle of a firefight to draw his own fucking blood…

He could feel whatever it was taking hold as she gently grasped the side of his face and requested he start counting backwards from one hundred.

Feeling more like Clint than Aaron right about then (holy shit he hated drugs) his lips turned up ever-so-slightly as he obeyed and started to count backwards… in Russian. He idly wondered what Natasha would say if she could see him (Clint shave you face it looks like something died there) and realized that these drugs must be good if he's going this out of it this quickly and shitshitshit—

Before his consciousness slipped entirely, he heard Phil's soft chuckle originating from the device planted in his molar, and he knew for sure that Natasha would hear about this.

E/N: So I was watching the Avengers the other day, and then I watched Bourne Legacy afterwards (I am going through a major Renner obsession at the moment) and realized… they could mesh together perfectly. It was like a beautiful light bulb moment, with the chorus of the angels and everything.

This was what my brain concocted as a result.

Summer, this is revenge for Before Letting Go and the emotional trauma you have subjected me to.